Root-End of a Wind Turbine Blade

ABSTRACT

The root-end of a blade of a wind turbine contains at least two segments. The segments contain a connection mechanism for their connection to build up the root-end. The segments contain a first segment section, which is prepared for a connection with fiber reinforced components of the blade. The segments contain a second segment section, which is prepared for a connection with a hub of a wind turbine or which is prepared for a connection with pitch-components of a wind turbine.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of European Patent Office applicationNo. 10167326.7 EP filed Jun. 25, 2010, which is incorporated byreference herein in its entirety.

FIELD OF INVENTION

The invention relates to a root-end of a blade of a wind turbine and toa wind-turbine blade, which contains this root end.

BACKGROUND OF INVENTION

There are a number of different methods, which are used to manufactureblades of a wind turbine.

It is known to wind roving tapes or roving bundles around a core ormandrel to build up a blade of a wind turbine.

It is also known to produce a blade by two pre-produced half-shells,which are connected. The half-shells are bonded (glued) together alongtheir respective leading and trailing edges. The half-shells are shapedin a way that a common cavity is built up by them within themanufactured blade. This cavity inside may be used to support a beam orthe like. The beam may be U-shaped or I-shaped and is used to connectthe half-shells by dedicated contact surfaces. Thisblade-production-method results in a heavy blade due to the needed glue.

A preferred method to manufacture a blade of a wind turbine is disclosedby document EP 1 310 351 A1. The blade is manufactured by help of aclosed-mould system. The blade is built up like a sandwich as describedbelow.

A first mould is used to support a number of stacked layers. The layersare put on top of the first mould and on top of each other to build upthe three-dimensional shape of the blade.

A cavity within the blade may be prepared by the usage of a balloon,which is filled with air for example. The balloon is embraced by thelayers and thus contributes to the three-dimensional shape of the blade.

It is even possible to locate pre-fabricated components within the bladestructure, for example along the leading and/or the trailing edge forreinforcement-purposes.

A second mould is connected with the first mould, thus aclosed-mould-system is achieved. The closed-mould system embraces thewhole blade-structure.

Air is evacuated out of the closed-mould-system, while resin is injectedinto the closed-mould-system. The resin cures out and the blade isnearly completed.

Now the balloons used may be removed out from the blade, thus acorresponding cavity remains inside the blade.

This blade-production procedure is also known as “Vacuum Assisted ResinTransfer Moulding, VARTM”-process.

Due to the stacked layers wrinkles may occur between and within theblade components. They may occur typically if fiber-mats are arranged ontop of each other or if fiber mats are located adjacent to rigidblade-components.

Document EP 1 109 657 A1 describes a method to produce closed compositestructures. Fiber reinforced material is placed around a molding coreand within a mould-system. The molding core is filled with a materialfor its shaping. After a curing process the filling material is removedout of the core and the whole molding core is even removed out from amould-system.

It is known that the root-end section of a blade, which is connectedwith the hub of the wind turbine directly or via components of apitch-system, needs to be very strong to cope with all forces acting onthe blade. The root-end also has to be designed as a rigid interface ofthe blade to the hub.

The root-end of the blade needs to be thick and massive, thus a lot oflayers and composite material needs to be arranged there.

The root-end of the blade is typically circular-shaped with a diameterof one meter up to five meters.

Due to this dimensions it is very difficult to manufacture the root-endwith a uniform thickness and without wrinkles.

Additionally it is very difficult to control and handle the castingprocess of the root-end. Due to its thickness and due to the used hugenumber of layers there the infusion and the distribution of resin withinthe root-end are very difficult.

The thick and massive structure of the root-end will contain a huge andlarge concentration of resin. Thus the root-end will become very hotwhile the resin cures out. This may result to a weak structure in thiscritical blade-area.

SUMMARY OF INVENTION

It is therefore the aim of the invention to provide an improved root-endof the blade and to provide an improved blade in view to the problems,which are addressed above.

This aim is achieved by the features the independent claims.

Preferred embodiments of the invention are object of the dependentclaims.

According to the invention a root-end of the blade is provided, whilethe root-end contains at least two segments.

The segments are preferably produced separately and are connected later,when the blade is manufactured.

The segments are designed, arranged and connected in a way that they areshaped as an appropriate root-end portion. This root-end portion is ableto cope with all forces, which might act on a blade, which contains thesegmented root-end.

The root-end segment is a pre-casted component preferably. It ispreferably manufactured by a VARTM-process, which uses a closed-mouldsystem.

Preferably the completed root-end shows a circular-shaped diameter, thuseach root-end segment is shaped like an arc of a circle.

Preferably the root-end is divided into six segments.

Adjacent segments are preferably fixed to each other to build up thecompleted root-end.

The fixation may contain a screw coupling or a dowel connection or thelike. A number of holes, which are allocated to surfaces of the adjacentsegments, may be used for the connection used.

Preferably each single root-end segment show a number of integratedresin channels. These channels are used to distribute a dedicated amountof resin to connect the root-end segment with the other blade componentsused. Thus a smaller amount of resin is needed and placed within theroot-end in view to the prior art described above.

Preferably each root-end segment contains a first segment section, whichis designed and developed for a connection with the other bladecomponents used.

Preferably this first segment is formed like a wedge. Thus a smoothconnection or transition of blade components (like fiber mats) with theroot-end segment is achieved while wrinkles are avoided within theblade-structure.

Preferably each root-end segment contains a second segment section,which is designed and developed for a connection of the completedroot-end with the hub or for a connection of the completed root-end withpitch-components being located asides the hub.

Preferably the segments of the root-end are positioned on a mould asdescribed in the introduction of this application.

Fiber reinforced material is placed around the root-end segments duringthe lay-up work, thus the root-end segments are an integrated part ofthe blade, which needs to be manufactured.

Thus the segments of the root-end become a fully integrated part of theblade, especially when the well-known VARTM-process is applied to theclosed-mould system to finish the blade.

Due to the invention it is very easy to align and to orientate thesegments within the blade-production process used.

If a VARTM-process is used tolerances of the closed mould system mightbe adjusted and balanced very easily.

The invention allows to lay-up two half-parts of a blade separately andin parallel. Each half-part comprises at least one pre-casted root-endsegment. Thus the two half-parts of the blade are built-up in parallel,resulting in a reduced amount of working-time needed.

These two half-parts might be brought together and onto a first mould asdescribed above, while fixation means and/or transportation means may beused for the positioning of the two half-parts of the blade. A secondmould is used to get the closed-mould-system, which embraces orincorporates the whole blade. Finally the VARTM-process may be appliedto the connected half-parts of the blade to finalize it in the wellknown “single shot” casting process.

It is also possible to manufacture two half parts of the blades by theVARTM-process, using at least one pre-casted root-end segment in each ofthe half parts. Finally the two half-parts of the blade might beconnected by help of glue or the like. Thus the production process isaccelerated in view to the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is shown in more detail by the help of the attachedfigures.

The figures show preferred configurations only and thus do not limit thescope of the invention.

FIG. 1 shows a preferred root-end segment according to the invention,

FIG. 2 shows a first mould-configuration to produce a root-end segmentinvented, and

FIG. 3 shows a second mould-configuration to produce another root-endsegment invented.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a preferred root-end segment S according to the invention.

This segment S is shaped and prepared to build up a circular shapedroot-end segment with five other segments.

If all six root-end segments S are connected the circular root-end isfinalized.

The segment S shows a number of resin channels RC. The resin channels RCallow the defined distribution of resin within the segment S and alongits surface.

These resin channels RC are used to distribute a dedicated amount ofresin to connect the root-end segment S with other blade componentsused. Thus a smaller amount of resin is needed and placed within theroot-end in view to the prior art described above.

The resin channels enable an easy control of the resin-infusion when theblade is manufactured by help of a VARTM-process for example.

Due to the reduced amount of resin needed the curing temperature is evenasides the root-end, while the blade is manufactured.

Preferably the blade is manufactured by a VARTM-process thus the segmentS is placed together with fiber mats and other blade components onto amould (not shown here). The fiber mats are placed to overlap at least apart of the segment S, thus the fiber mats are used connect the segmentS with other blade components.

The segment S shows a first segment section SSB, which is designed anddeveloped for a connection of the segment S with the other bladecomponents—like the fiber mats used.

Preferably this first segment section SSB is formed like a wedge. Thus asmooth connection or transition of the fiber mats with the root-endsegment S is achieved. Wrinkles are avoided within the blade-structuredue to this smooth transition.

This wedge-shape provides a gradually transition zone from the root-endportion to the rest of the blade structure.

Preferably the segment S contains a second segment section SSH. Thissection SSH is designed and developed for a connection of the completedblade via its root-end with a wind-turbine hub or for a connection ofthe completed blade via its root-end with pitch-components, which arelocated asides the hub for example.

This interface SSH to the hub comprises a number of circumferentialconnection holes, which are prepared for a connection with the flange ofthe hub for example or with the flange of a dedicated pitch-component.

For the fixation of the segment S with other adjacent segments a numberof holes H are prepared within a surface of the segment S. The holes arepart of a bolted connection or of a dowel connection or the like.

The segment S shown in FIG. 1 covers a 60° segment of a circle of acompleted root-end-portion, thus six segments S are needed to build upthe whole root-end.

FIG. 2 shows a first mould-configuration MS180 to produce a root-endsegment as invented.

The mould-configuration MS180 is designed and used to produce ormanufacture a root-end segment as a pre-casted component.

This pre-casted component will cover a 180° segment of a circle of acompleted root-end-portion, thus two segments are needed to build up acompleted root-end.

The mould-configuration MS180 is preferably used within a VARTM-processto manufacture the segment. Thus a number of fiber mates FML is put aslayers on top of the mould-configuration MS180. Thus themould-configuration MS180 is used as lower first mould, which supportsall needed, segment components (as fiber mats for example).

Another appropriate mould is used later to achieve the closed-mouldsystem for the VARTM-process as described in the introduction of thisapplication.

FIG. 3 shows a second mould-configuration MS60 to produce anotherroot-end segment invented.

The mould-configuration MS60 is designed and used to produce ormanufacture a root-end segment as a pre-casted component.

This pre-casted component will cover a 60° segment of a circle of acompleted root-end-portion, thus six segments are needed to build up acompleted root-end.

The mould-configuration MS60 is preferably used within a VARTM-processto manufacture the segment. Thus a number of fiber mates FML is put aslayers on top of the mould-configuration MS60. Thus themould-configuration MS60 is used as lower first mould, which supportsall needed segment components (as fiber mats for example).

Another appropriate mould is used later to achieve the closed-mouldsystem for the VARTM-process as described in the introduction of thisapplication.

It is very easy to lay up the fiber mats FML in this mould MS60 comparedwith the mould MS180.

The lay-out-work in the mould MS60 is less tedious than in the MS180.

Within the MS180 it is more difficult to obtain a uniform thickness andto avoid wrinkles, as the fiber mats FML tend to hang like curtains.They might not follow exactly the shape of the inner-mould MS180, thuspockets and resin rich areas in the casted component may be the result.

Thus the quality of the segments, which are manufactured by help of themould MS60, is improved in view to the segments, which are manufacturedby help of the mould MS180.

It has to be noted that there is at least one another way to manufacturesegments for the root-end-portion of the blade (not shown here).

For example a one-piece root-end may be produced like this: a fiber isspun around a cylinder or around another shaped surface. The root-endportion is casted to get a stable root-end-portion. The root end is cutnow into a number of root-end segments (for example into a number oftwo, four or six segments). Thus production time is reducedconsiderably, while wrinkles are eliminated by this method.

1.-11. (canceled)
 12. A root-end of a blade of a wind-turbine,comprising: a plurality of segments, each of the plurality of segmentscomprise a connection mechanism to connect to an adjacent segment of theplurality of segments in order to form the root-end, a first segmentsection, which is prepared for a connection with fiber reinforcedcomponents of the blade, a second segment section, which is prepared fora connection with a hub of a wind turbine or which is prepared for aconnection with pitch-components of a wind turbine.
 13. The root-endaccording to claim 12, wherein each of the plurality of segments is apre-casted component.
 14. The root-end according to claim 12, whereinthe connected segments of segments root-end form a circular-shapeddiameter.
 15. The root-end according to claim 12, wherein the root-endcomprises six segments.
 16. The root-end according to claim 12, whereinthe root-end comprises four segments.
 17. The root-end according toclaim 12, wherein the root-end comprises two segments.
 18. The root-endaccording to claim 12, wherein the adjacent segments are connected by ascrew connection.
 19. The root-end according to claim 12, wherein theadjacent segments are connected by a dowel connection.
 20. The root-endaccording to claim 12, wherein each of the plurality of segmentsincludes a hole used for the connection of the adjacent segments. 21.The root-end according to claim 12, wherein each of the plurality ofsegments contain a plurality of resin channels as an integral part. 22.The root-end according to claim 12, wherein the first segment section isshaped like a wedge to achieve a smooth transition zone between thefiber reinforced components of the blade and the segment.
 23. Theroot-end according to claim 12, wherein the plurality of segments of theroot-end are positioned on a mould, which is used to support thesegments and other blade components for an applied VARTM-process tomanufacture a wind turbine blade.
 24. Root-end according to claim 23,wherein a fiber reinforced material is arranged and/or placed around theplurality of segments, thereby making the plurality of segments anintegral part of the blade.
 25. A blade of a wind-turbine, comprising: asegmented root-end according claim 12.